Photothermic relay and control system



Jan. 6, 1959 l G. KosLOw 2,367,703

PHOTOTHERMIC RELAY AND CONTROL SYSTEM Filed'march 25, 1957 2sheets-sheet 1 IN VEN TOR. 6501266 osLoA/ Jan. 6, 1959 G, KOSLQW2,867,703

PHOTOTHERMIC RELAY AND CONTROL SYSTEM Filed March 25, 1957 a`sheets-sheet 2 PHUTTHERMIC RELAY AND CONTROL SYSTEM George Koslow, NewYork, N. Y.

Application March 25, 1957, Serial No. 648,433

6 Claims. (Cl. 200-138) This invention relates to a thermally actuatedapparatus vwhich may be utilized for system control and alarmpurposes'and has particular application in those situations where timedelay in actuating the mechanism is not an important factor or wheresuch time delay is deslred.

The apparatus of the present invention employs a conventional heatdetector or sensing element toward which is directed a source of highXed intensity radiant energy whereby under'normal conditions theapparatus is inoperative, but upon total or partial interruption of saidradiation for sufficient time the heat sensing eie- Inent operates toactuate an electric switch, set o an alarm, or otherwise relay or recordthe detected interruption of radiant energy, or mechanically operate asuitable control device. For example, the detector may be of the uniorbimetallic type in which case, if desired, the metallic element may bearranged to operate as an inverse thermoswitch under the foregoingconditions whereby to break an electric circuit and shut down anelectrically operated mechanism.

One such arrangement is in connection with a conveyor system wherein theinterruption of the radiant energy for a preselected length of time bythe jamming up of conveyed objects actuates an alarm or shuts down theconveyor system, or both.

Another use, as illustrated in the accompanying drawings, is as a smokealarm or control system for oil and coal burners wherein the emittedsmoke in the breech, stack or flue interrupts or absorbs the radiantenergy and accordingly actuates a bimetallic switch, damper orindicator. In such cases, the delayed response of the present apparatusis desirable in that such delay prevents false signals, as when smoke istemporarily given off upon starting up an oil burner or adding freshcoal or fuel to a furnace. rl`his arrangement can be kused to signal orindicate malfunction of the furnace, improper combustion, fuel waste,and, more importantly, a violation of laws respecting smoke control andair pollution. In the last-mentioned application, the apparatus may bearranged to automatically shut down an oil burner` as well as ring analarm if smoking persists beyond the legal limit.

The nature of the invention and its advantages will be more readilyunderstood from the following description of several embodiments thereofwith reference to the accompanying drawings wherein: t

Fig. 1 is a diagrammatic view of one form of the invention arranged inconnection with a smoke alarm system for a coal fired furnace;

Fig. 2 is an enlarged elevation of the smoke stack of the furnace ofFig. 1, taken on the line 2--2 of Fig. l; Fig. 3 is an enlargedelevation of the bimetallic switch .of Fig. 1 as used with the presentinvention;

Fig. 4 is a side View of the switch taken on the line 4-4 of Fig. 3;

Fig. 5 is an elevation of another type of bimetallic relay embodying amicroswitch.

2,867,703 itatented v dan. y6, `1959 -alined, flanged tubular extensionsor openings 3. A companion flange 4 having a plate glass window 5 issecured or mounted on each extension 3 by any suitable means such asbolt and nut assemblies 6. This arrangement provides a transparenttransverse opening in the stack 2 for a purpose to be describedhereinafter. In cases where forced or mechanical draft systems are notused, windowed companion anges 4 may be omitted.

A conventional electric reflector spot lamp 7, connected by cable 8 to asource of current (not shown), is so mounted that its light beam isdirected through the transverse openings 3 of the furnace stack 2 towarda radiant heat detector such as the bimetallic switch or relay 9connected in series with a battery 10 which provides the operatingvoltage for an alarm bell 11. In this particular arrangement, thecontacts of the bimetallic switch remain open as long as the spot lamp 7is lit and the light beam is not interrupted by smoke. Since the sourceof radiant energy is of fixed intensity, it is obvious that barringinterruption of the path between the lamp 7 and bimetallic switch 9, thecontacts of the latter will remain open thus rendering the alarm circuitinoperative. However, should the furnace begin to emit smoke through itsstack 2, said smoke will create a relatively opaque or dense medium inthe path of the radiant heat, thereby absorbing a portion of saidradiant energy and resulting in a drop in temperature at the bimetallicswitch 9. This will cause the switch contacts to close and energize thealarm circuit. The switch 9 is so constructed that there is anappreciable time delay during the interruption of the radiant energydirected thereto before the contacts are closed, thereby insuring thatthe alarm will be actuated only upon a prolonged smoking condition ofthe furnace. This obviates the possibility of setting of the alarmduring the brief period of smoke emission which often ensues uponstoking the furnace.

Referring to Figs. 3 and 4, there is shown one form of bimetallic switchor relay usable with the present invention.` The switch comprises a pairof bimetallic plates or elements 12 and 13, each being composed of twothin strips of metal having disparate thermal coefficients. The

f plates are supported at their lower ends from a bracket 14 by means ofa bolt and nut assembly 15, said bolt and nut being suitably insulatedfrom the metal members of the switch 9 by any suitable means, such as aninsulating sleeve (not shown). Spacing and insulating washers 16insulate the elements from one another and from the support bracket 14.Switch element 12 is provided with an adjustable screw type contact 17,and element 13 is provided with a contact bead 1?. The lower ends of theelements 12 and 13 are provided with leads aser/,ros

consequently is the only element bent to the left, thereby causingcontacts 17 and 18 to remain open. Upon interruption of the source ofradiant heat as described previously, element 13 will cool and bend tothey right, thereby closing the switch contacts 17 and 18 andenergizing'the alarm circuit. Both switch elements 12 and 13 are made ofthe same bimetallic materials whereby variation in ambient temperatureis lautomatically compensated for, thus limiting the actuation of theswitch solely to conditions of lessened intensity of the radiant energydirected toward element 13. As stated, element 12 is shielded from thesource of radiant energy by bracket 14. The receiving surface of element13 may be blackened or coated with other heat absorbing material toincrease its efficiency. The other surface of element 13, the adjacentsurface of element l2, and both surfaces of bracket 14 are preferablycoated with a bright aluminized or other reflective material. The outersurface of element 12 is preferably blackened to help radiate any heatthat may leak in through conduction.

`The speed of response of the switch can be altered by changing suchvariables as the receiving area of element 13, the operating temperatureof lamp 7, the mass of the switch elements 12 and 13, yand by variousother modications well known in the art. ln addition, the radiant energysource may be any type of electrically heated element, such as thefilament of an infra-red lamp or of an ordinary incandescent lamp 7 asillustrated. Additionally, other rellective or refractive means may beemployed for more accurate direction arid concentration of the radiantenergy.

ln the modied form of the switch shown in Fig. 5, a microswitch 21 isutilized as the circuit closing member, the microswitch being providedwith leads 22 and 23 for connection to the alarm circuit. The switch ismounted on bimetallic element 24 and is actuated by the adjustablecontact screw 25 of bimetallic element 26. Elements 24 and 26 andsupporting and shielding bracket 27 are constructed and arranged tocooperate as in the previously described embodiment of the invention. Ofcourse, elements 24 -and 26 and bracket 27 need only be thermallyinsulated since they are not incorporated in the electric circuit. rtheadvantage of the microswitch is its ability to handle heavy currents andhigh voltages, permitting it to turn off an oil burner directly andsimultaneously ring an alarm through the optional use of 4a double-throwswitch.

Fig. 6 shows a conventional heat detector 28 as modified to provideadditional advantages when embodied in the present invention. Thedetector 2S is one of the several types in wide application aselectrically operated thermal time-delay relays. As shown, twobimetallic elements 29 and 30 are provided, element 30 serving as anambient correction. The elements 29 and 30 are mounted on a shieldingsupport bracket 31 xedly secured in an octyl base 32 provided with maleplug fittings 33 for insertion into the receptacle of an electriccircuit, in this case preferably the same circuit supplying the sourceof radiant energy. A wire wound ceramic heating element 34 is mountedadjacent element 36 as shown for a purpose to be described. A glass domeor bulb 35 suitably encloses the various elements. Current is suppliedto bimetallic switch elements 29 and 3@ and to heating element 34through lead wires 36, 37, 38 and 39 which pass through the base member32 and are appropriately connected to plugs 33.

As embodied in the photothermic vrelay system of the present invention,the heater 34 provides line voltage correction and a means forexternally adjusting the temperature at which the switch contactsoperate. When used as a smoke alarm, the contacts may be adjusted. tooperate .at `the desired smoke density. The output of energy from theradiant source depends on the same line voltage as does .the heatingelement 34, and since cooling or heating both bimetallic elements 29 and30 causes them to move in the same direction under simultaneous changesin the operating temperature of the radiant source and the heatingelement 34, line vvoltage changes will have negligible effect upon theoperation of the switch. The temperature of the heater 34 can beadjusted with a rheostat, variable transformer, or other means toregulate the operating range of the switch contacts. Otherwise, theheating element may be an externally located lamp or the like connecteddirectly to the line, the adjustment being accomplished by varying thedistance of the lamp from the switch elements.

Some advantages of the foregoing arrangement are freedom from -chillingby sudden drafts, contact protection, line voltage and ambientcorrection, external adjustment of sealed components, and plug-in foreasy replacement. The glass dome 35 may be eliminated. Many othervariations will become obvious to those skilled in the art of existingequipment.

Numerous variations in the types of heat sensing elements will beobvious to those skilled in the art. For example, the sensing elementsmay be unimetallic, and the element for ambient correction may bedispensed with. A liquid filled bulb may be used as the heat detectingor sensing element. These elements enable heat to be converted intomechanical movement to operate a switch, tip a mercury switch, ordirectly operate `a valve, damper, pointer or indicator, recording pen,etc. A thermocouple is another suitable element, the electrical outputof which may be used to operate a meter, relay or recorder.

Fig. 7 shows how vthe present invention may be used to directly andmechanically control the damper setting in a furnace stack or flue. Asillustrated, furnace flue 2, transverse anged openings 3, windowedcompanion flanges 4 and spot lamp 7 are constructed and arranged tocooperate as in the previously described embodiment of the invention.The heat sensing element 4t) is of the simple bimetallieor thermostatictype. The thermostat 4t) is suitably supported on a bracket 41 by meansof bolt `and-nut assembly 42 and is mechanically coupled at its upperend through suitable linkages, as by linking rods 43 and 44, to a damper45 pivotally supported in the flue 2 in the conventional manner. By thismeans the movement of the thermostat during excessive smoking in thetlue is mechanically communicated to the damper 45 and actuates or openssaid damper to permit increased Hue draft.

Fig. 8 shows the-invention utilized in connection with f a smoke oropacity indicator. The furnace flue 2, openings 3, windowed .flanges 4and spot lamp 7 are cooperatively arranged as previously described. Asimple bimetallic element 46 is utilized as the heat sensing element.Element 46- is supported from a bracket by means of bolt and nutassembly 47. The bracket 48 is provided with an upright arm 49 to whichis secured a graduated scale 50 by means of bolt and nut assembly S1.The scale may be calibrated in degrees of smoke density in the flue 2. Apointer 52 brazed or otherwise connected to thermostatic element 46 isarranged and adapted to traverse the scale 5t) as the element 46 bendsto and fro under varying conditions of smoke density in the flue.

The embodiments of Figs. 7 and 8 may be rened by including additionalbimetallic elements or the equivalents thereof for ambient correction.

It is thus seen that there is provided a relativelysimple andinexpensive apparatus for system control and alarm purposes whichrequires no special skills to install and operate.'

While there has been described above the principles of- What is claimedis:

1. A smoke detecting apparatus for a furnace provided with a smoke stackhaving a pair of diametrically opposed openings therein, comprising, incombination, a source of radiant heat of fixed intensity directedthrough the openings of said stack, a heat responsive bimetallic relayexposed to said directed heat, said relay being responsive to anincrease in the opacity of the heat transmitting medium upon theemission of smoke through said stack, and mechanical means connected toand operated by said relay for positively communicating the movementthereof.

2. The apparatus according to claim l, wherein the communicating meansincludes a pointer mounted on the relay, said pointer being associatedwith a scale.

3. The apparatus according to claim l, wherein the communicating meansincludes a link element connecting the relay to a damper in the furnacestack.

4. A thermally actuated control or alarm apparatus comprising, incombination, a source of radiant heat of xed intensity, a heatresponsive relay exposed in the direction of said source `of radiantheat and responsive to variation in the opacity of the heat transmittingmedium, said relay including a bimetallic plate composed of strips ofmetal having disparate thermal coeicients,

a second bimetallic plate having the same thermal characteristics as thebimetallic plate of the relay, said second plate being in spacedconfronting relation to said relay plate, a shielding plate disposedbetween said bimetallic plates whereby said second bimetallic plate isshielded from the source of radiant heat, a device mounted on saidsecond plate and mechanically actuated by the movement of the relay tocommunicate said movement in response to variation in opacity of theheat transmitting medium.

5. The apparatus according to claim 4, wherein the device actuated Ibythe relay is a switch which controls a source of electrical energy.

6. The apparatus according to claim 5, wherein the switch is amicroswitch References Cited in the tile of this patent UNITED STATESPATENTS 878,456 Darwin Feb. 4, 1908 1,167,045 Cade et al Ian. 4, 19162,063,997 Godsey Dec. 15, 1936 2,159,392 McCabe May 23, 1939 2,371,590Brooke et al t- Mar. 13, 1945 2,441,025 Logan May 4, 1948 2,502,844Hildreth Apr. 4, 1950

